High voltage solid-state switches, such as the gated diode switch (GDS) and the thyristor, which are both essentially p-i-n diodes, when in the on and conducting state, are characterized by dual carrier injection and typically use a shield region around the n cathode in order to increase the operating voltage range. Typically, the anode and cathode regions of the GDS have a rectangular shape, as does the shield region surrounding the cathode. The on resistance of the gated diode switch, though relatively low, is still not as low as is desirable in some applications. One contributing cause to the on resistance of the GDS is that the emitting efficiency of the cathode is significantly below that of the anode because of the shield region.
The radial gated diode switch (RGDS), which is described in copending U.S. patent application, Ser. No. 448,631, now U.S. Pat. No. 4,573,065 filed Dec. 10, 1982, and having a common assignee with the present application and two common inventors, uses anode, cathode, shield, and gate regions which each have a side portion that is an arc of one of a plurality of concentric circles. The RGDS has less on resistance that a conventional GDS of the same area.
In some applications, even lower on resistance than that of the above-described RGDS is desirable.